In switched capacitor circuits an analogue switch is typically used to switch a capacitor. An op-amp is typically used to implement an integration step of the analogue switch.
Voltage spikes associated with the op-amp circuitry give rise to integration errors, the voltage spikes being sampled and aliased into low frequencies, where they can no longer be filtered out with a high frequency filter.
A known method to reduce the integration error due to voltage spikes is based on using a fully differential op-amp and a sampling circuit, which benefits from the fact that the majority of spikes are common mode and have a small differential component.
However, a problem with this arrangement is that for certain applications requiring high levels of oversampling such as sigma-delta converters and low-pass filters, the differential method cannot provide sufficient spike protection, giving rise to serious integration errors.
This invention seeks to provide a compensating circuit which mitigates the above mentioned disadvantages.